This invention relates generally to protection systems for electrically powered or dependent appliances or equipment, such as computers, televisions, stereos, microwaves and the like, which are susceptible to damage from high intensity transient line events, i.e., power surges, caused by lightning strikes or ground fault events. More particularly, the invention relates to such systems where the equipment is isolated from the AC power grid when a transient event occurs and backup power from storage cells is instantaneously supplied to the equipment such that operations are not interrupted. Even more particularly, the invention relates to such systems where the equipment is isolated and the auxiliary power is supplied upon the detection of a high intensity electromagnetic frequency (EMF) burst from a lightning strike which has occurred at a relatively remote distance before the storm is within range to damage the equipment.
Modern electronic and electrically powered equipment are very susceptible to damage from transient line events, often referred to generally as power surges. These transient line events can be caused by power grid loss, local transformer breakdown, switching surges and load inducing events. Probably the most damaging high intensity transient line events are those caused by nearby lightning strikes during a storm, whether in the form of direct strikes to a power grid or as a result of the electromagnetic field of nearby strikes. Conventional devices to protect equipment from damage from transient line events include fuses, circuit breakers and surge suppressor devices. These devices react to the transient line event itself, in that the protective action is not initiated until the power surge or spike reaches the device, and are often inadequate to protect highly sensitive electronic equipment from damage from the intense power level and rise time of a lightning strike--i.e., the equipment is already damaged before the protective device can react.
In order to address the problem of lightning strikes, it is an object of this invention to provide a protective system which is initiated well in advance of any lightning derived transient line events affecting the equipment being protected. This and other objects, which will be clear from the subsequent discussion, are accomplished by providing a system which detects the occurrence of lightning strikes at a relatively remote distance and before any power surge or spike resulting from a lightning strike can be delivered to the equipment through the AC power grid. When a strike is detected which meets the criteria of the system, the equipment is immediately isolated from the AC power grid and auxiliary power converted from DC storage cells is supplied to operate the equipment without interruption. After a predetermined time period with no further lightning strikes, the equipment is reconnected to the AC power grid. It is a further object to provide such a system which can also detect non-lightning induced transient line events and respond in the same manner by isolating the equipment and supplying auxiliary power. It is a further object to provide such a system where the distant lightning strike can be detected in various ways.